1. Field of the Invention
This invention relates to waste disposal systems, and more particularly, to a refractory hearth system of the type which includes a rotary turntable upon which is deposited organic material to be incinerated, and thereby reduced to ashes and/or simpler organic components.
2. Brief Description of the Prior Art
A number of types of rotary hearth furnaces which utilize rotating heated surfaces and material treatment methods have been heretofore used, as well as proposed. Some of these systems are large, heavy and expensive permanent installations used in industrial processes in which very large volumes of material to be treated are continuously charged to the furnace and the products of treatment continuously removed therefrom. In some installations, a rotary hearth furnace is used to incinerate organic waste materials and thereby reduce such waste to a more easily and safely disposable form. In other systems, the furnace is particularly designed and used for calcining or for dehydrating inorganic materials.
One of the more recent proposals for a rotary hearth furnace of the type described is that which is set forth in Stribling, U.S. Pat. No. 3,605,656. The structure disclosed in the Stribling patent is used for burning waste products, including partially compressed sludge cakes from sewage processes as well as refuse from municipalities. A rotary, refractory lined hearth is provided which has a central axial discharge for moving ash materials through a tubular vertical discharge pipe at the center of the hearth turntable. The organic materials to be incinerated are charged to the outer periphery of the rotary hearth, and a plurality of plows are disposed over the upper surface of the hearth. These plows function to sequentially direct the organic material carried on the upper surface of the hearth toward the central axial discharge pipe at the center of the hearth. The plows can be varied in their angular relationship above the hearth to selectively provide for one or several revolutions of the material being incinerated prior to its discharge at the center of the hearth. Tangential combustion air inlets and burners are provided around and over the hearth to provide for the heating of the material on the upper surface of the hearth.
In Martin, U.S. Pat. No. 2,676,006, organic material to be incinerated is introduced to the top of a rotary, refractory lined turntable via a duct adjacent the outer periphery of the turntable. A central axial discharge chute is provided at the center of the hearth, with such discharge chute or duct passing through a gas seal trap into a collection duct. Martin, like Stribling, employs tangential burners firing into the enclosed chamber above the rotating hearth. A plurality of rabble blades are provided over the rotating hearth to deflect deposited materials carried on the hearth in a radially inward direction so that ultimately, after one or a plurality of revolutions, the incinerated material will be discharged through the axially discharging duct at the center of the furnace.
Other patents which disclose various constructions of rotary hearth furnaces include U.S. Pat. No. 1,436,520 to Oliver, in which a rotary hearth within a refractory lined hood is provided for the purpose of calcining hydromagnesite; U.S. Pat. No. 630,510 to Keiper in which a rotary hearth-type furnace is provided for roasting ores; U.S. Pat. No. 551,342 in which a plurality of vertically tiered hearth plates are employed in conjunction with scraper blades acting on garbage sequentially deposited on the several plates for the purpose of cremating the garbage; Lewers, U.S. Pat. No. 2,061,708, and Ab-der Halden, U.S. Pat. No. 1,878,581; in which a revolving hearth cooperates with stationary rakes and also with blades or vanes to both stir a material carried on the hearth for incineration purposes, and move it radially inwardly toward a central axial discharge opening in the hearth.